This review article provides an overview of the synthesis and reactivity of low-oxidation state metalate anions of d-block elements, with a focus on contributions reported between 2006 and 2-2022. The field has seen significant advancements due to advanced concepts in complex synthesis and ligand design. The potential of highly reactive metalate complexes in small molecule activation and homogeneous catalysis has become increasingly evident. The article is divided into four main sections: introduction, synthesis and basic reactivity patterns of d-block metalates, reactivity of metalates toward small inorganic molecules, and a summary and outlook. The first section introduces the concept of low-valent transition metalates, emphasizing their highly electron-rich nature and potential applications in chemical transformations. The second section details the synthetic routes and ligand frameworks used to stabilize these metalates, including carbonyls, isocyanides, alkenes, polyarenes, phosphines, phosphorus heterocycles, amides, and redox-active nitrogen-based ligands. It also highlights the importance of ion-pairing interactions and metal–metal bonding in stabilizing low-valent metalates. The third section discusses the reactivity of metalates toward small inorganic molecules such as H₂, N₂, CO, CO₂, and P₃. It showcases impressive catalytic properties in hydrogenation, N₂ activation, CO activation, and phosphorus activation, highlighting the potential of transition metalate anions in challenging catalytic processes. The fourth section provides a summary and outlook, emphasizing the growing interest in low-valent transition metalates and their applications in organic synthesis and energy conversion. The review aims to serve as a valuable resource for researchers interested in this dynamic field.This review article provides an overview of the synthesis and reactivity of low-oxidation state metalate anions of d-block elements, with a focus on contributions reported between 2006 and 2-2022. The field has seen significant advancements due to advanced concepts in complex synthesis and ligand design. The potential of highly reactive metalate complexes in small molecule activation and homogeneous catalysis has become increasingly evident. The article is divided into four main sections: introduction, synthesis and basic reactivity patterns of d-block metalates, reactivity of metalates toward small inorganic molecules, and a summary and outlook. The first section introduces the concept of low-valent transition metalates, emphasizing their highly electron-rich nature and potential applications in chemical transformations. The second section details the synthetic routes and ligand frameworks used to stabilize these metalates, including carbonyls, isocyanides, alkenes, polyarenes, phosphines, phosphorus heterocycles, amides, and redox-active nitrogen-based ligands. It also highlights the importance of ion-pairing interactions and metal–metal bonding in stabilizing low-valent metalates. The third section discusses the reactivity of metalates toward small inorganic molecules such as H₂, N₂, CO, CO₂, and P₃. It showcases impressive catalytic properties in hydrogenation, N₂ activation, CO activation, and phosphorus activation, highlighting the potential of transition metalate anions in challenging catalytic processes. The fourth section provides a summary and outlook, emphasizing the growing interest in low-valent transition metalates and their applications in organic synthesis and energy conversion. The review aims to serve as a valuable resource for researchers interested in this dynamic field.